Duplexer having transmit and receive sections mounted on a single substrate

Abstract

A duplexer usable for both transmission and reception in a mobile communication apparatus such as a car phone has both its transmission section and reception section mounted on a single substrate. The transmission section is connected between an input terminal and an antenna terminal and includes an isolator and either a circuit having only inductors and capacitors or a trap circuit having a dielectric resonator and an inductor and a II-type low-pass filter having an inductor and capacitors. The reception section is comprised of a filter using dielectric resonators.

What is claimed is: 
     
       1. A duplexer comprising: a transmission section consisting of an isolator and a transmission circuit devoid of any resonators and comprising inductors and capacitors;   a reception section comprising a reception filter having a dielectric resonator apparatus; and   a single substrate on which said transmission and reception sections are mounted, said transmission circuit functioning to match said isolator with said reception filter.   
     
     
       2. The duplexer of claim 1 wherein said transmission section consists of said isolator and a transmission circuit consisting of inductors and capacitors, wherein said reception section consists of said reception filter, and wherein said reception filter consists of dielectric resonators and capacitors. 
     
     
       3. The duplexer of claim 2 wherein said inductors and capacitors of said transmission circuit are connected such that said transmission circuit comprises a π-type low-pass filter having an inductor and capacitors and a series-connected resonance circuit having an inductor and a capacitor. 
     
     
       4. The duplexer of claim 2 further comprising an antenna terminal, an input terminal and an output terminal, said transmission section being connected between said antenna terminal and said input terminal, said reception section being connected between said antenna terminal and said output terminal. 
     
     
       5. The duplexer of claim 4 wherein said inductors and capacitors of said transmission circuit are connected such that said transmission circuit comprises a π-type low-pass filter having an inductor and capacitors and a series-connected resonance circuit having an inductor and a capacitor. 
     
     
       6. The duplexer of claim 1 further comprising an antenna terminal, an input terminal and an output terminal, said transmission section being connected between said antenna terminal and said input terminal, said reception section being connected between said antenna terminal and said output terminal. 
     
     
       7. The duplexer of claim 6 wherein said inductors and capacitors of said transmission circuit are connected such that said transmission circuit comprises a π-type low-pass filter having an inductor and capacitors and a series-connected resonance circuit having an inductor and a capacitor. 
     
     
       8. The duplexer of claim 1 wherein said inductors and capacitors of said transmission circuit are connected such that said transmission circuit comprises a π-type low-pass filter having an inductor and capacitors and a series-connected resonance circuit having an inductor and a capacitor. 
     
     
       9. The duplexer of claim 1 further comprising grounding electrodes formed on surfaces of said single substrate. 
     
     
       10. A duplexer comprising: a transmission section comprising an isolator, a trap circuit having a single dielectric resonator and a capacitor, and a π-type low-pass filter having an inductor and capacitors;   a reception section comprising a reception filter having a dielectric resonator apparatus; and   a single substrate on which said transmission and reception sections are mounted, said transmission circuit functioning to match said isolator with said reception filter.   
     
     
       11. The duplexer of claim 10 wherein said reception section consists of said reception filter, and wherein said reception filter consists of dielectric resonators and capacitors. 
     
     
       12. The duplexer of claim 11 further comprising an antenna terminal, an input terminal and an output terminal, said transmission section being connected between said antenna terminal and said input terminal, said reception section being connected between said antenna terminal and said output terminal. 
     
     
       13. The duplexer of claim 10 further comprising an antenna terminal, an input terminal and an output terminal, said transmission section being connected between said antenna terminal and said input terminal, said reception section being connected between said antenna terminal and said output terminal. 
     
     
       14. The duplexer of claim 10 further comprising grounding electrodes formed on surfaces of said single substrate.